It turns out that people are more dangerous to wildlife than massive radioactive contamination. Chernobyl is now at or rapidly approaching the wildlife diversity of a protected nature reserve, and several endangered species have been seen making their home there - one of which was previously undiscovered. Only the most radioactive sites continue to resist the encroachment of nature - the rest of it has become a haven for endangered species.
http://www.wired.com/magazine/2011/04/ff_chernobyl/all/